Power board, on-board connector, lighting device, display device and television receiver

ABSTRACT

In a power board, relay terminals penetrate a circuit board through fitting holes, and are connected to output terminals. The fitting holes are thus formed as through holes on the circuit board, and thereby on-board connectors provided for connection to the relay terminals on a chassis can be arranged on the back surface of the circuit board on the opposite side of the chassis. Electronic components free from restriction of the positional relationship with the chassis can be mounted on the back surface of the circuit board, as are the on-board connectors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power board, an on-board connector, a lighting device, a display device and a television receiver.

2. Description of the Related Art

An example of a lighting device capable of functioning as a backlight for a liquid crystal display device is disclosed in JP-A-2004-294592. The lighting device has a construction in which relay terminals are mounted into through holes formed on a chassis that has a substantially flat plate-shaped configuration and functions as a reflector plate. An electrode portion of a discharge tube arranged on the front side of the chassis and a power board arranged on the back side of the chassis are connected to each relay connector, so that the discharge tube can receive the power supply from the power board via the relay terminal.

In the power board described in JP-A-2004-294592, electronic components are mounted on the surface of a circuit board on the opposite side of the chassis, while an output terminal to be fitted to the relay terminal is mounted on the chassis-facing surface. In the case that components are thus mounted to both surfaces of the circuit board, there is no choice but to use reflow soldering as a soldering method for fixing the components to the circuit board, because solder dipping that involves dipping of the circuit board in a molten solder bath cannot be applied.

However, the reflow soldering cannot be applied to a circuit board formed of a material sensitive to high temperature (e.g., a phenolic paper-base copper-clad laminated board), because a reflow oven is heated to a high temperature. That is, in the case of a circuit board formed of a material sensitive to high temperature, components cannot be mounted to both surfaces of the circuit board, and therefore the components should be mounted on one surface of the circuit board.

In this case, in order to achieve an output terminal provided on the chassis-facing side of the circuit board as in JP-A-2004-294592 for connection to the relay terminal, the components on the circuit board are limited to being mounted on the chassis-facing surface.

SUMMARY OF THE INVENTION

In view of the foregoing circumstances, preferred embodiments of the present invention enable a surface of a single-sided power board on the opposite side of a chassis, when the power board is connected to a relay terminal on the chassis, to define a single mounting surface.

A power board according to a preferred embodiment of the present invention, which is to be mounted to the back side of a chassis having a substantially plate-shaped configuration, includes a circuit board capable of being arranged substantially parallel to the chassis, and an on-board connector mounted to the circuit board. The output terminal of the on-board connector can be connected to a relay terminal provided on the chassis, so that power is supplied to a discharge tube arranged on the front side of the chassis. A fitting hole is formed through the circuit board so as to extend from the front surface to the back surface thereof. The on-board connector is mounted to the back surface of the circuit board, and is positioned to correspond to the fitting hole.

The relay terminal and the output terminal can be connected to each other, while one or both thereof penetrate the circuit board through the fitting hole. The fitting hole is thus formed as a through hole on the circuit board, and thereby the on-board connector, provided for connection to the relay terminal on the chassis, can be arranged on the back surface of the circuit board on the opposite side of the chassis. On the other hand, electronic components free from restriction of the positional relationship with the chassis can be mounted on the back surface of the circuit board, as is the on-board connector. According to a preferred embodiment of the present invention, the power board connected to the relay terminal on the chassis can be thus achieved as a single-sided power board in which the back surface on the opposite side of the chassis is provided as the single mounting surface.

In the power board described above, the on-board connector can include a housing made of an insulating material, so that the output terminal is at least partly held in the housing.

In this case, the output terminal is at least partly held in the housing, and therefore the portion held in the housing can be prevented from interference with foreign substances.

In the power board described above, an engaging recess having an opening corresponding to the fitting hole can be formed on the housing, so that the output terminal is arranged in the engaging recess.

In this case, the relay terminal can be inserted into the engaging recess so as to be connected to the output terminal therewithin. Thereby, the connection between the terminals can be prevented from interference with foreign substances.

In the power board described above, a positioning portion, which can lock the output terminal so that displacement of the output terminal along the inside surface of the engaging recess is restricted, may be provided on the inside surface.

In this case, the displacement of the output terminal is restricted by the positioning portion, and therefore the flexural rigidity of the output terminal is not required to be increased for displacement prevention. The reduced flexural rigidity of the output terminal, thus provided, results in reduction of the frictional resistance developed when the relay terminal is connected to the output terminal. Thus, the operational efficiency at the time of connection can be improved.

In the power board described above, the output terminal can include a proximal portion fixed to the housing, a flexible portion extending from the proximal portion and being capable of elastic deflection, and a connecting portion extending from the flexible portion and having a substantially U-shaped configuration capable of elastically pinching the relay terminal. The connecting portion may include two strip portions, so that a free-end-side strip portion of the two strip portions on the opposite side of the flexible portion can have contact with the relay terminal.

If the relay terminal moves or displaces from the output terminal toward the flexible portion side, the whole connecting portion moves to the flexible portion side, together with the relay terminal. Thus, the connection between the relay terminal and the free-end-side strip portion can be maintained. If the relay terminal moves or displaces from the output terminal to the free end side or to the opposite side of the flexible portion, the free-end-side strip portion of the connecting portion is pushed by the relay terminal into movement. Then, the connection between the relay terminal and the free-end-side strip portion can be also maintained.

In the power board described above, in a case where a plurality of on-board connectors as the above on-board connector are arranged in a line so as to be capable of corresponding to a plurality of relay terminals as the above relay terminal, the output terminal can include a connecting portion that is elongated in a direction substantially perpendicular to the array direction of the on-board connectors. The connecting portion can have contact with the relay terminal that preferably has a plate-shaped configuration having a width larger than that of the connecting portion and to be arranged parallel or substantially to the array direction of the on-board connectors.

In the case of including a plurality of on-board connectors arranged in a line so as to correspond to a plurality of relay terminals, the output terminals of the on-board connectors may be displaced in the array direction from the relay terminals due to some reason such as the difference in thermal expansion rate between the circuit board as a mounting base for the on-board connectors and the chassis as a mounting base for the relay terminals. In view of this, according to a preferred embodiment of the present invention, the connecting portion is provided on the output terminal so as to be elongated in a direction substantially perpendicular to the array direction of the on-board connectors, while the relay terminal having a plate-shaped configuration, wider than the connecting portion and to be arranged substantially parallel to the array direction of the on-board connectors, is arranged so as to be capable of contact with the connecting portion. The relay terminal is preferably large in width along the array direction, and therefore the connection between the relay terminal and the connecting portion can be maintained even if the relay terminal is displaced in the array direction from the output terminal.

In the power board described above, the on-board connector can be arranged along an edge portion of the circuit board. The output terminal may be arranged on an area of the housing on the opposite side of the edge portion, so that a sectional arrangement is provided.

In this case, the output terminal is arranged on the area of the housing on the opposite side of the edge portion of the circuit board, resulting in sectional arrangement. Consequently, a low-voltage area is left on a portion of the on-board connector located in proximity to the edge portion of the circuit board.

An on-board connector according to a preferred embodiment of the present invention is provided, which is to be mounted to a circuit board in order to provide a power board. The power board can be mounted to the back side of a chassis having a substantially plate-shaped configuration, so that the circuit board is arranged substantially parallel to the chassis. The on-board connector includes an output terminal that can be connected to a relay terminal provided on the chassis so that power is supplied to a discharge tube arranged on the front side of the chassis. The on-board connector can be mounted to the back surface of the circuit board, and be positioned to correspond to a fitting hole that is formed through the circuit board so as to extend from the front surface to the back surface thereof.

The relay terminal and the output terminal can be connected to each other, while one or both thereof penetrate the circuit board through the fitting hole. The fitting hole is thus formed as a through hole on the circuit board, and thereby the on-board connector, provided for connection to the relay terminal on the chassis, can be arranged on the back surface of the circuit board on the opposite side of the chassis. On the other hand, electronic components free from restriction of the positional relationship with the chassis can be mounted on the back surface of the circuit board, as is the on-board connector. According to a preferred embodiment of the present invention, the power board connected to the relay terminal on the chassis can be thus achieved as a single-sided power board in which the back surface on the opposite side of the chassis is provided as the single mounting surface.

The on-board connector, described above, can further include a housing made of an insulating material, so that the output terminal is at least partly held in the housing.

In this case, the output terminal is at least partly held in the housing, and therefore the portion held in the housing can be prevented from interference with foreign substances.

In the on-board connector described above, an engaging recess, having an opening capable of being arranged to correspond to the fitting hole, can be formed on the housing, so that the output terminal is arranged in the engaging recess.

In this case, the relay terminal can be inserted into the engaging recess so as to be connected to the output terminal therewithin. Thereby, the connection between the terminals can be prevented from interference with foreign substances.

In the on-board connector described above, a positioning portion, which can lock the output terminal so that displacement of the output terminal along the inside surface of the engaging recess is restricted, may be provided on the inside surface.

In this case, the displacement of the output terminal is restricted by the positioning portion, and therefore the flexural rigidity of the output terminal is not required to be increased for displacement prevention. The reduced flexural rigidity of the output terminal, thus provided, results in reduction of the frictional resistance developed when the relay terminal is connected to the output terminal. Thus, the operational efficiency at the time of connection can be improved.

In the on-board connector described above, the output terminal can include a proximal portion fixed to the housing, a flexible portion extending from the proximal portion and being capable of elastic deflection, and a connecting portion extending from the flexible portion and having a substantially U-shaped configuration arranged to elastically pinch the relay terminal. The connecting portion may include two strip portions, so that a free-end-side strip portion of the two strip portions on the opposite side of the flexible portion can have contact with the relay terminal.

If the relay terminal moves or is displace from the output terminal toward the flexible portion side, the whole connecting portion moves to the flexible portion side, together with the relay terminal. Thus, the connection between the relay terminal and the free-end-side strip portion can be maintained. If the relay terminal moves or displaces from the output terminal to the free end side or to the opposite side of the flexible portion, the free-end-side strip portion of the connecting portion is pushed by the relay terminal into movement. Then, the connection between the relay terminal and the free-end-side strip portion can be also maintained.

In the on-board connector described above, in a case where a plurality of housings as the above housing are arranged in a line so as to be capable of corresponding to a plurality of relay terminals as the above relay terminal, the output terminal can include a connecting portion that is elongated in a direction substantially perpendicular to the array direction. The connecting portion can have contact with the relay terminal that preferably has a plate-shaped configuration having a width larger than that of the connecting portion and to be arranged parallel or substantially parallel to the array direction.

In the case of including a plurality of on-board connectors arranged in a line so as to correspond to a plurality of relay terminals, the output terminals of the on-board connectors may displace in the array direction from the relay terminals due to some reason such as the difference in thermal expansion rate between the circuit board as a mounting base for the on-board connectors and the chassis as a mounting base for the relay terminals. In view of this, according to a preferred embodiment of the present invention, the connecting portion is provided on the output terminal so as to be elongated in a direction substantially perpendicular to the array direction of the on-board connectors, while the relay terminal having a plate-shaped configuration, wider than the connecting portion and to be arranged parallel or substantially parallel to the array direction of the on-board connectors, is arranged so as to be capable of contact with the connecting portion. The relay terminal preferably has a large width along the array direction, and therefore the connection between the relay terminal and the connecting portion can be maintained even if the relay terminal displaces in the array direction from the output terminal.

In the on-board connector described above, the housing can be arranged along an edge portion of the circuit board. The output terminal may be arranged on an area of the housing that can be positioned on the opposite side of the edge portion, so that a sectional arrangement is provided.

In this case, the output terminal is arranged on the area of the housing that can be positioned on the opposite side of the edge portion of the circuit board, resulting in sectional arrangement. Consequently, a low-voltage area is left on a portion of the on-board connector located in proximity to the edge portion of the circuit board.

A lighting device according to a preferred embodiment of the present invention includes a power board according to a preferred embodiment of the present invention described above, a chassis and a discharge tube.

A display device according to another preferred embodiment of the present invention includes a lighting device according to a preferred embodiment of the present invention described above, and a display panel arranged on the front side of the lighting device.

A television receiver according to yet another preferred embodiment of the present invention includes a display device according to another preferred embodiment of the present invention described above.

These and other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a horizontal sectional view of a display device according to preferred embodiment 1 of the present invention.

FIG. 2 is a perspective view of a lighting device.

FIG. 3 is a rear view of the lighting device.

FIG. 4 is a perspective view of a power board.

FIG. 5 is a front view of the power board.

FIG. 6 is a perspective view of an on-board connector.

FIG. 7 is a perspective view of the on-board connector.

FIG. 8 is a front view of the on-board connector.

FIG. 9 is a front view of the on-board connector into which a relay connector is fitted.

FIG. 10 is a horizontal sectional view of the on-board connector.

FIG. 11 is a horizontal sectional view showing the on-board connector mounted to a lamp unit.

FIG. 12 is a partially-enlarged sectional view of the lamp unit.

FIG. 13 is a partially-enlarged front view of the lighting device.

FIG. 14 is a perspective view of a relay connector.

FIG. 15 is a perspective view of a discharge tube.

FIG. 16 is an exploded perspective view of a television receiver.

FIG. 17 is a front perspective view of a lighting device according to preferred embodiment 2 of the present invention.

FIG. 18 is a front view of the lighting device.

FIG. 19 is a perspective view of relay connectors.

FIG. 20 is a partially-enlarged front view showing a connecting structure between a relay connector and a discharge tube.

FIG. 21 is a side view of a relay connector.

FIG. 22 is a sectional view showing that a ferrule on a discharge tube is capable of engaging with a stopper.

FIG. 23 is a sectional view showing a connecting structure between a relay connector and a power board.

FIG. 24 is a perspective view of a discharge tube.

FIG. 25 is a rear view of a ferrule.

FIG. 26 is a plan view of the ferrule.

FIG. 27 is a side view of the ferrule.

FIG. 28 is a rear perspective view of the lighting device.

FIG. 29 is a front view of a lighting device according to preferred embodiment 3 of the present invention.

FIG. 30 is a front view showing the lighting device, from which discharge tubes are detached.

FIG. 31 is a rear view of the lighting device.

FIG. 32 is a perspective view of a grounding member.

FIG. 33 is a perspective view of a grounding terminal.

FIG. 34 is a sectional view showing that a ferrule on a discharge tube is capable of engaging with a stopper.

FIG. 35 is a partially-enlarged front view showing a connecting structure between a grounding terminal and a discharge tube.

FIG. 36 is a perspective view showing a modification of a ferrule.

FIG. 37 is a side view of FIG. 36.

FIG. 38 is a perspective view of a grounding terminal.

FIG. 39 is a sectional view showing a connection between a grounding terminal shown in FIG. 38 and a ferrule.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred Embodiment 1

Preferred embodiment 1 according to the present invention will be hereinafter explained with reference to FIGS. 1 to 16.

Overview of Display Device D

A display device D shown in FIG. 16 is a so-called liquid crystal display device including a display panel 11 and a lighting device 10 as shown in FIG. 1, which preferably has a horizontally-elongated rectangular shape as a whole. The display panel 11 is disposed on the front side of the lighting device 10, so that the lighting device 10 as a backlight can illuminate the display panel 11 from the back side. The display device D can be applied to a television receiver. As shown in FIG. 16, the television receiver includes the display device D, and front and back cabinets Ca and Cb capable of holding the display device D therebetween. Further included are a power source P other than a power board 16 described below, a tuner T and a stand S. FIG. 1 schematically shows the display device D, and therefore the shapes of relay connectors 14, on-board connectors 18 and the like differ slightly from those in the other figures.

The display panel 11 has a well-known construction, in which liquid crystal as a material with an optical property that changes with applied voltage is disposed in the gap between a transparent TFT substrate and a transparent CF substrate. TFTs (Thin Film Transistors), as switching elements connected to a source wiring line and a gate wiring line running at right angles to each other, and pixel electrodes connected to the TFTs are provided on the TFT substrate. A color filter, on which color sections of three primary colors, i.e., Red (R), Green (G) and Blue (B), are arranged in a matrix, is provided on the CF substrate.

Overview of Lighting Device 10

As shown in FIGS. 2 and 3, the lighting device 10 includes a lamp unit 12 and power boards 16. The lamp unit 12 includes a metallic chassis 13, which preferably has a substantially horizontally-elongated rectangular plate-shaped configuration and functions as a reflector plate. Further included are a plurality of discharge tubes 15 held in a horizontal position and vertically arranged on the front side of the chassis 13 so as to be parallel or substantially parallel to one another, and a plurality of relay connectors 14 which are vertically arranged along the lateral edges of the chassis 13 so as to correspond to the discharge tubes 15. The power boards 16 are disposed on the back side of the chassis 13 so as to supply power to the discharge tubes 15 via the relay connectors 14.

A plurality of mounting holes 13H corresponding to the ends of the discharge tubes 15 are formed through the chassis 13 so as to extend from the front side to the back side, and are vertically arranged so as to be level with the respective discharge tubes 15. The relay connectors 14 are mounted through the respective mounting holes 13H (See FIGS. 12 and 13). As shown in FIG. 14, each relay connector 14 includes a holder 20 made of synthetic resin, and a metallic relay terminal 30 housed in the holder 20.

A pair of upper and lower elastic retaining portions 25 and a pair of right and left engaging surfaces 26 are provided on the outer surface of the holder 20. The holder 20 is inserted into the mounting hole 13H from the front side of the chassis 13, and is fixed to the chassis 13 due to the engaging surfaces 26 in abutting contact with the opening edge of the mounting hole 13H on the front surface of the chassis 13 and due to the retaining protrusions of the elastic retaining portions 25 being locked by the opening edge of the mounting hole 13H on the back surface of the chassis 13. When attached to the chassis 13, the front end portion of the holder 20 projects to the front side of the chassis 13, while the back end portion of the holder 20 projects to the back side of the chassis 13.

A container room 23 is formed in the projecting portion of the holder 20 on the front side of the chassis 13, by removing the front surface and one lateral surface thereof. A plate-like wall portion 27 is provided on the projecting portion of the holder 20 on the back side of the chassis 13. The relay terminal 30 is disposed in the holder 20. The relay terminal 30, which can be formed by bending a metallic plate that is formed into a predetermined shape by punching, for example, includes a tube connecting portion 31 having a pair of upper and lower elastic nipping portions 32 including plates having a substantially circular arc shape, and further includes a plate-like board connecting portion 33 projecting to the back side. The tube connecting portion 31 is disposed in the container room 23, while the board connecting portion 33 is arranged along the wall portion 27.

Referring to FIG. 15, each discharge tube 15 preferably is formed of a cold cathode fluorescent tube that includes a generally elongated straight glass tube 40 having a circular cross section, elongated outer leads 42 which have a circular cross section and project linearly from the respective ends of the glass tube 40 and coaxially with the glass tube 40, and further includes ferrules 50 attached to the respective end portions of the glass tube 40. Each ferrule 50, which can be formed by bending or hammering a metallic (e.g., copper alloy) plate that is formed into a predetermined shape by punching, for example, includes a body 51 and a conductive portion 57. The body 51 preferably has a substantially cylindrical shape, which is attached on the outer circumference of the glass tube 40. The conductive portion 57 extends from the end edge of the body 51 so as to have elastic contact with the outer periphery of the outer lead 42, and is fixed by welding. The discharge tube 15 is mounted to the chassis 13, so that the end portions thereof are fitted into the container rooms 23 of the holders 20 while tube connecting portions have elastic contact with the outer circumferences of the bodies of the ferrules 50.

Overview of Power Board 16

As shown in FIGS. 4 and 5, each power board 16 includes a circuit board 17 having a circuit provided on its back surface (i.e., the surface on the opposite side of the chassis 13), electronic components 19 mounted on the back surface of the circuit board 17, and a plurality of on-board connectors 18 mounted on the back surface of the circuit board 17.

The circuit board 17 preferably has a vertically-elongated rectangular shape as a whole, and is formed using a phenolic paper-base copper-clad laminated board (known as a phenolic paper). A plurality of fitting holes 17H having a vertically-elongated rectangular shape are formed through the circuit board 17 so as to extend from the front side to the back side. The plurality of fitting holes 17H are arranged vertically along the lateral edge portion 17E (or side edge portion) of the circuit board 17 so as to correspond to the above-described relay terminals 30 (or relay connectors 14). Further, a plurality of positioning holes 17 a are formed through the circuit board 17 so as to extend from the front side to the back side. The positioning holes 17 a are arranged between the fitting holes 17H and the side edge of the circuit board 17 so that a pair of upper and lower positioning holes corresponds to each fitting hole 17H.

Overview of On-Board Connector 18

Referring to FIGS. 9 to 11, the on-board connectors 18 are arranged along the lateral edge of the circuit board 17 so as to correspond to the respective fitting holes 17H, and are engaged with the respective relay connectors 14 through the fitting holes 17H. As shown in FIGS. 6 to 8, each on-board connector 18 includes a housing 60 made of an insulating material such as a synthetic resin, and further includes a metallic output terminal 70 completely contained in the housing 60.

Housing 60

The housing 60 preferably is a single-piece component that includes a terminal holding portion 61 and an insulating portion 62. The terminal holding portion 61 defines a block-shaped configuration, in which an engaging recess 63 is formed so as to have a vertically-elongated rectangular opening on the outer surface (i.e., the circuit board 17 facing surface) of the housing 60. The position and size of the engaging recess 63, when the on-board connector 18 is mounted to the circuit board 17, are set to correspond substantially to those of the fitting hole 17H. The relay connector 14 can be fitted into the engaging recess 63. In the engaging recess 63, a pair of upper and lower positioning portions 64 preferably include rib-like protrusions arranged to protrude from the inside surface closer to the edge portion 17E of the circuit board 17. The pair of positioning portions 64 are vertically located at substantially the center of the engaging recess 63.

Further, a holding groove 65, in which the output terminal 70 is mounted (or held), is provided within the terminal holding portion 61. The holding groove 65 is formed so as to traverse the engaging recess 63 and have an elongated opening extending on the circuit board 17 facing surface of the housing 60 and along the horizontal direction perpendicular or substantially perpendicular to the edge portion 17E of the circuit board 17. The holding groove 65 includes a first groove portion 65 a formed of a deep recess on the inside surface of the engaging recess 63 farther from the edge portion 17E of the circuit board 17, a pair of second groove portions 65 b formed of recesses extending to the respective upper and lower sides from the far end portion (i.e., the end portion farthest from the edge portion 17E) of the first groove portion 65 a, and a third groove portion 65 c formed of a recess extending between the pair of positioning portions 64 from the inside surface of the engaging recess 63 closer to the edge portion 17E of the circuit board 17.

The terminal holding portion 61 is formed to be larger than the insulating portion 62, described below, in thickness measured from the back surface of the circuit board 17, so that a substantially step-shaped structure is formed therebetween. A tapered surface 61S is formed on the outer surface of the terminal holding portion 61 on the opposite side of the circuit board 17, by cutting the edge of its insulating portion 62 side corner at an angle of 45°.

The insulating portion 62 is arranged closer to the edge portion 17E of the circuit board 17 than the terminal holding portion 61, so as to be continuous with the edge portion 17E side surface of the terminal holding portion 61. The circuit board 17 facing surface of the insulating portion 62 is continuous and flush with the circuit board 17 facing surface of the terminal holding portion 61. The insulating portion 62 is the same as the terminal holding portion 61 in width (i.e., length along the vertical direction parallel to the edge portion 17E of the circuit board 17). The upper and lower outer surfaces of the insulating portion 62 are continuous and flush with the respective upper and lower outer surfaces of the terminal holding portion 61. The horizontal length (i.e., length along a direction perpendicular or substantially perpendicular to the edge portion 17E of the circuit board 17) of the insulating portion 62 is substantially half the horizontal length of the terminal holding portion 61. The insulating portion 62 includes a pair of upper and lower thin-walled portions 62 a having a block-shaped configuration, and further includes a thick-walled portion 62 b arranged between the thin-walled portions 62 a and having a block-shaped configuration. The insulating portion 62, when viewed from the edge portion 17E side of the circuit board 17, defines a laterally facing T-shape. Metallic reinforcing pins 66, elongated perpendicularly or substantially perpendicularly to the back surface of the circuit board 17, are embedded in the respective thin-walled portions 62 a. One end portion of each reinforcing pin 66 projects from the circuit board 17 facing surface of the thin-walled portion 62 a to the outside, and is fitted into the positioning hole 17 a. The fitting structure between the reinforcing pin 66 and the positioning hole 17 a serves as a reinforcing mechanism to fix the housing 60 to the circuit board 17. A positioning recess 62 c is formed on the thick-walled portion 62 b so as to have a circular opening on its outer surface on the opposite side of the circuit board 17. The positioning recess 62 c serves as a positioning means, when a cover not shown, or the like, is mounted to the power board 16 from the back side. The axis thereof is perpendicular to the back surface of the circuit board 17.

Output Terminal 70

Referring to FIGS. 7 to 11, the output terminal 70, which can be formed by bending a metallic plate that is formed into a predetermined shape by punching, for example, includes a proximal portion 71, a supported portion 74, a flexible portion 72 and a connecting portion 73. The output terminal 70 is mounted into the holding groove 65 from the circuit board 17 facing side of the terminal holding portion 61.

The proximal portion 71 preferably has a rectangular plate-shaped configuration elongated in a direction perpendicular or substantially perpendicular to the back surface of the circuit board 17, so that the surface thereof is arranged substantially parallel to the edge portion 17E of the circuit board 17. A connecting pin 71 a having a small width is provided on the proximal end of the proximal portion 71. The proximal portion 71 is held in the second groove portion 65 b by press fitting, while small protruding portions formed on the lateral edge portions of the proximal portion 71 wedge into the inner walls of the second groove portions 65 b. Consequently, the output terminal 70 is held so as to be substantially completely contained in the terminal holding portion 61, except for the connecting pin 71 a. The connecting pin 71 a penetrates through a connecting hole 17 b of the circuit board 17, and is connected to the circuit. The housing 60 is fixed to the circuit board 17 due to the connecting pin 71 a fitted into the connecting hole 17 b.

The supported portion 74 preferably has an elongated shape having a width smaller than that of the proximal portion 71, and is arranged in the deep portion of the first groove portion 65 a, i.e., arranged away from the opening thereof. The supported portion 74 extends substantially perpendicularly from the end portion of the proximal portion 71 on the opposite side of the connecting pin 71 a toward the edge portion 17E side of the circuit board 17. That is, the supported portion 74 is elongated in a direction substantially parallel to the back surface of the circuit board 17 and substantially perpendicular to the edge portion 17E of the circuit board 17. The supported portion 74 is smaller than the proximal portion 71 in length.

The flexible portion 72 preferably has an elongated shape having the same width as the supported portion 74, and extends substantially perpendicularly (or substantially parallel to the proximal portion 71) from the distal end (i.e., the end portion on the opposite side of the proximal portion 71) of the supported portion 74. The flexible portion 72 preferably is slightly smaller than the proximal portion 71 in length. The flexible portion 72 is held in the first groove portion 65 a, so as to be capable of being slanted at an acute or obtuse angle to the supported portion 74, due to its elastic deformation.

The connecting portion 73 preferably has a substantially elongated shape having the same width as the flexible portion 72, and specifically defines a substantially U-shaped configuration having a narrowed open end. The connecting portion 73 includes a first strip portion 73 a that loops back at the distal end of the flexible portion 72 and extends in a direction away from the circuit board 17, and further includes a second strip portion 73 b that loops back at the distal end of the first strip portion 73 a and extends in a direction toward the circuit board 17. On the connecting portion 73, the distance between the strip portions 73 a, 73 b is partly set to be shorter. The shorter-distance portions of the strip portions 73 a, 73 b are located in the engaging recess 63. The first strip portion 73 a is arranged along the inside surface of the engaging recess 63 farther from the edge portion 17E of the circuit board 17, so as to be partly contained in the first groove portion 65 a. The second strip portion 73 b is arranged along the inside surface of the engaging recess 63 closer to the edge portion 17E of the circuit board 17, so as to be partly contained in the third groove portion 65 c (or partly arranged between the pair of positioning portions 64).

The power board 16, thus constructed, is mounted to the chassis 13 by being moved toward the chassis 13 from the back side while the circuit board 17 is kept parallel to the chassis 13. The mounting direction of the on-board connectors 18 to the relay connectors 14 is directly opposite to the mounting direction of the discharge tube 15 to the relay connectors 14. That is, the fitting direction of the on-board connectors 18 is parallel or substantially parallel to the mounting direction of the discharge tube 15 to the relay connectors 14. At the time of fixation, the wall portion 27 of each relay connector 14 and the board connecting portion 33 arranged along the wall portion 27 penetrate the circuit board 17 through the fitting hole 17H, and are inserted into the engaging recess 63 of the on-board connector 18 so as to be placed between the first strip portion 73 a and the second strip portion 73 b, as shown in FIGS. 9 and 11. Consequently, the wall portion 27 has contact with the first strip portion 73 a, while the board connecting portion 33 has contact with the second strip portion 73 b. Further, the connecting portion 73 deforms elastically so as to increase the distance between the first strip portion 73 a and the second strip portion 73 b. The relay connector 14 is thus fitted into the on-board connector 18, and thereby the relay terminal 30 is conductively connected to the output terminal 70. Consequently, the power board 16 is connected to the discharge tubes 15 via the relay connectors 14, so that the power from the power board 16 can be supplied to the discharge tubes 15. When the on-board connectors 18 have reached a proper state of being fitted onto the relay connectors 14, the power board 16 is screwed to the chassis 13. Note that the relay terminal 30 is movably fitted into the engaging recess 63. That is, it is fitted as shown in FIG. 9 so that the clearance space 27 c is left between the relay terminal 30 and the engaging recess 63. The dimensions of the relay terminal 30 and the output terminal 70 are designed so that the connection therebetween can be maintained even when the relay terminal 30 moves or displaces within the engaging recess 63. Specifically, the margin (or allowance) for connection between the board connecting portion 33 and the connecting portion 73 is preferably larger than the width of the clearance space 27 c.

Operational Effects of the Present Preferred Embodiment

The fitting holes 17H are formed as through holes on the circuit board 17. This enables the on-board connectors 18, provided for connection to the relay terminals 30 on the chassis 13, to be arranged on the back surface of the circuit board 17 on the opposite side of the chassis 13. On the other hand, the electronic components 19 free from restriction of the positional relationship with the chassis 13 can be mounted on the back surface of the circuit board 17, as are the on-board connectors 18. Thus, according to a preferred embodiment of the present embodiment, the power board 16 connected to the relay terminals 30 on the chassis 13 can be achieved as a single-sided power board in which the back surface on the opposite side of the chassis 13 is provided as the single mounting surface.

The output terminal 70 is completely contained in the housing 60 (except for the connecting pin 71 a), and thereby can be protected from interference with extraneous or foreign substances.

The relay terminal 30 is inserted into the engaging recess 63 so as to be connected to the output terminal 70 therewithin. Thereby, foreign substances are prevented from interference with the connection between the relay terminal 30 and the output terminal 70.

The output terminal 70 is locked by the positioning portions 64 provided on the inside surface of the engaging recess 63, so that displacement of the output terminal 70 in the vertical direction parallel to the edge portion 17E of the circuit board 17 is restricted. Therefore, the flexural rigidity of the output terminal 70 is not required to be increased for displacement prevention. The reduced flexural rigidity of the output terminal 70, thus provided, results in reduction of the frictional resistance developed when the relay terminal 30 is connected to the output terminal 70. Thus, the operational efficiency when the relay terminal 30 is connected to the output terminal 70 can be improved.

The output terminal 70 is formed to include a proximal portion 71 fixed to the housing 60, a flexible portion 72 extending from the proximal portion 71 (via the supported portion 74) and capable of elastic deflection, and a substantially U-shaped connecting portion 73 extending from the flexible portion 72 and capable of elastically pinching the relay terminal 30. The board connecting portion 33 of the relay terminal 30 can have contact solely with the second strip portion 73 b of the two strip portions 73 a, 73 b of the connecting portion 73, i.e., the free-end-side strip portion on the opposite side of the flexible portion 72.

According to the construction, if the board connecting portion 33 of the relay terminal 30 relatively moves toward the flexible portion 72 side within the engaging recess 63, the whole connecting portion 73 (i.e., both of the first strip portion 73 a and the second strip portion 73 b) moves to the flexible portion 72 side (or to the proximal portion 71 side), together with the board connecting portion 33, while pushing the flexible portion 72 into elastic deflection. Thus, the connection between the board connecting portion 33 and the second strip portion 73 b can be maintained.

Conversely, if the board connecting portion 33 relatively moves to the free end side or to the opposite side of the flexible portion 72, the second strip portion 73 b on the free end side is pushed by the relay terminal 30 into movement, without noticeable elastic deflection of the flexible portion 72. Then, the connection between the board connecting portion 33 and the second strip portion 73 b can be also maintained. Note that the first strip portion 73 a at the time is disengaged from the wall portion 27.

In the construction that includes a plurality of on-board connectors 18 and a plurality of relay terminals 30 arranged in lines, the output terminals 70 may displace in the array direction from the relay terminals 30 due to some reason such as the difference in thermal expansion rate between the nonmetallic circuit board 17 as a mounting base for the on-board connectors 18 and the metallic chassis 13 as a mounting base for the relay terminals 30.

In view of this, as shown in FIG. 9, the connecting portion 73 is provided on the output terminal 70 so as to be elongated in a direction substantially perpendicular to the array direction of the on-board connectors 18 (i.e., in the direction perpendicular to the plane of FIG. 9), while the board connecting portion 33 is arranged on the relay terminal 30 to define plate-shaped configuration parallel or substantially parallel to the array direction of the on-board connectors 18 (i.e., the vertical direction in FIG. 9) and can be larger than the connecting portion 73 in width (i.e., length along a direction parallel or substantially parallel to the array direction of the on-board connectors 18). The board connecting portion 33 is arranged to have contact with the connecting portion 73.

According to the construction, the board connecting portion 33 is preferably large in length along the array direction of the on-board connectors 18, and therefore the connection between the board connecting portion 33 and the connecting portion 73 can be maintained even if the relay terminal 30 displaces in the array direction from the output terminal 70.

In view of a high voltage applied to the output terminal 70 of the on-board connector 18 arranged along the edge portion 17E of the circuit board 17, a leak may occur between the output terminal 70 and an electrical conductor approaching the edge portion 17E of the circuit board 17.

For this reason, in the present preferred embodiment, the output terminal 70 is surrounded by the synthetic-resin housing 60, in which the output terminal 70 is held in the terminal holding portion 61 arranged across the insulating portion 62 from the edge portion 17E of the circuit board 17. Thus, the output terminals 70 are positioned in areas of the housings 60 on the opposite side of the edge portion 17E, resulting in narrow sectional arrangement. Thereby, a low-voltage area is left on a portion (i.e., the insulating portion 62) of the on-board connector 18 located in proximity to the edge portion 17E of the circuit board 17, and a long distance is maintained between the output terminal 70 and the edge portion 17E of the circuit board 17. Therefore, even when an electrical conductor approaches the edge portion 17E of the circuit board 17, a leak between the output terminal 70 and the electrical conductor can be prevented.

On the housing 60, the insulating portion 62, which is arranged closer to the edge portion 17E of the circuit board 17 and does not include the output terminal 70, preferably has a substantially block-shaped configuration provided continuously along the substantially entire width of the housing 60. Thereby, foreign substances can be reliably prevented from approaching the output terminal 70 side from the edge portion 17E of the circuit board 17.

The insulating portion 62 of the housing 60, which is arranged closer to the edge portion 17E of the circuit board 17 and does not include the output terminal 70, can effectively function as a positioning element arranged to position the housing 60 on the circuit board 17.

The output terminal 70 preferably has an elongated shape substantially perpendicular to the edge portion 17E of the circuit board 17, and is positioned, in the width direction (or vertical direction) parallel or substantially parallel to the edge portion 17E of the circuit board 17, so as to be at substantially the center of the housing 60. Thereby, foreign substances can be prevented from approaching the output terminal 70 from either upper side or lower side of the housing 60, resulting in prevention of a leak caused by the approach.

On the housing 60, the terminal holding portion 61 provided for arrangement of the output terminal 70 is preferably larger than the insulating portion 62 uninvolved in arrangement of the output terminal 70, in thickness measured from the circuit board 17, so that a step-shaped structure is provided therebetween. Therefore, the shape and/or size of the output terminal 70 can be set with increased flexibility.

The edge portion of the terminal holding portion 61 on the insulating portion 62 side is cut into a tapered shape. Therefore, when a cover is attached to the on-board connectors 18, the opening edge of the cover is prevented from catching on the housing 60.

The connecting portion 73 of the output terminal 70, provided as a connecting mechanism to connect to the outside (i.e., to the relay terminal 30), cannot be covered up with the housing 60, for functional reasons. However, the connecting portion 73 is arranged in the engaging recess 63. Therefore, the connecting portion 73 is less subject to a leak, compared to arranging a connecting portion 73 on the outer surface of the housing 60.

Preferred Embodiment 2

Next, preferred embodiment 2 of the present invention will be explained with reference to FIGS. 17 to 28. In the preferred embodiment 2, the construction of the lighting device 110 of a display device D differs from that of preferred embodiment 1. The other constructions are similar to preferred embodiment 1. Therefore, the same constructions are designated by the same symbols, and explanations for the constructions, operations and effects thereof are omitted.

Overview of Lighting Device 110

The lighting device 110 includes a lamp unit 112 and power boards 116, as shown in FIGS. 17 and 28. The lamp unit 112 includes a metallic chassis 113, which preferably has a horizontally-elongated rectangular plate and functions as a reflector plate. Further included are a plurality of discharge tubes 115 held in a horizontal position and vertically arranged on the front side of the chassis 113 so as to be parallel or substantially parallel to one another, and a plurality of relay connectors 114 which are vertically arranged along the lateral edges of the chassis 113 so as to correspond to the discharge tubes 115. The power boards 116 are disposed on the back side of the chassis 113 so as to supply power to the discharge tubes 115 via the relay connectors 114.

A plurality of substantially rectangular mounting holes 113H corresponding to the ends of the discharge tubes 115 are formed through the chassis 113 so as to extend from the front side to the back side, and are vertically arranged to be level with the respective discharge tubes 115. The relay connectors 114 are mounted through the respective mounting holes 113H (See FIGS. 22 and 23).

Relay Connector 114

As shown in FIGS. 19 to 21, each relay connector 114 includes a holder 120 made of synthetic resin, and a relay terminal 131 that is housed in the holder 120 and made of metal (e.g., stainless steel).

The holder 120 includes a box-shaped portion 121 that preferably has a block-shaped configuration as a whole, and further includes a wall portion 122 that projects backward from the back surface of the box-shaped portion 121.

A container room 123 is formed in the box-shaped portion 121, so as to have an opening extending from the front side to the lateral side (i.e., the lateral side on the opposite side of the lateral edge portion of the chassis 113). The front opening portion of the opening of the container room 123 is provided as a receiving opening 124, into which an end portion (or ferrule 136) of the discharge tube 115 is fitted from the front side. The lateral opening portion is provided as an escape opening 125 for preventing interference with the glass tube 134 when the end portion of the discharge tube 115 is held in the container room 123. A stopper 126 is provided on the escape opening 125, so as to bulge inward from the opening edge and form a plate-shaped configuration. Due to the stopper 126, the escape opening 125 is narrowed so as to form a substantially U-shaped opening. The vertical size of the substantially U-shaped escape opening 125 is preferably smaller than the inner diameter of the body 137 of the ferrule 136 and be equal to or slightly larger than the outer diameter of the glass tube 134 of the discharge tube 115. On the escape opening 125, a concave portion 127 having a semicircular shape is formed on the far end portion of the opening edge. The radius of curvature of the concave portion 127 is preferably equal to or slightly larger than the radius of curvature of the outer circumference of the glass tube 134. On the escape opening 125, a pair of upper and lower guiding portions 128 are formed on areas of the opening edge on the front side of the concave portion 127.

On the box-shaped portion 121, an extended portion 129 extending parallel or substantially parallel to the chassis 113 is formed on the lateral surface of the box-shaped portion 121 that includes the escape opening 125. The extended portion 129 extends so as to separate the front surface of the chassis 113 from the escape opening 125. A pair of upper and lower retaining protrusions 130 are formed on the outer surface (i.e., upper surface and lower surface) of the box-shaped portion 121.

The relay terminal 131 is held within the holder 120. The relay terminal 131 can be formed by bending a metallic plate that is formed into a predetermined shape by punching, for example. The relay terminal 131 includes a pair of vertically symmetrical elastic pressing portions 132 preferably defined by curved plates, and further includes a board connecting portion 133 defined by a flat plate-like portion that projects to the back side. The pair of elastic pressing portions 132, which are housed in the container room 123, can deflect elastically and vertically so as to increase distance therebetween. The vertical distance between the pair of elastic pressing portions 132 is shortest at a position corresponding to the front side of the concave portion 127 of the stopper 126. The minimum distance between the elastic pressing portions 132, when the elastic pressing portions 132 are not forced into elastic deflection or are in a free state, is preferably smaller than the outer diameter of the body 137 of the ferrule 136 attached on the discharge tube 115. On the other hand, the board connecting portion 133 projects from the back surface of the box-shaped portion 121 so as to be exposed to the outside of the holder 120, and extends backwards along the wall portion 122.

When the relay connector 114 is mounted to the chassis 113, the wall portion 122 of the holder 120 is inserted into a mounting hole 113H from the front side of the chassis 113 as shown in FIGS. 22 and 23. Thereby, the outer surface of the box-shaped portion 121 comes in contact with the opening edge of the mounting hole 113H on the front surface of the chassis 113, while the retaining protrusions 130 are locked by the opening edge of the mounting hole 113H on the back surface of the chassis 113. Thus, the chassis 113 is sandwiched between the outer surface of the box-shaped portion 121 on the front side and the retaining protrusions 130 on the back side. Thereby, the holder 120 is fixed to the chassis 113 so that its movement in the mounting direction (i.e., the through direction of the mounting hole 113H) is restricted. Then, the mounting of the relay connector 114 to the chassis 113 is completed. When the relay connector 114 is attached to the chassis 113, the box-shaped portion 121 as the front end portion of the holder 120 projects (or is exposed) to the front side of the chassis 113 while the wall portion 122 as the back end portion of the holder 120 projects (or is exposed) to the back side of the chassis 113.

Discharge Tube 115

Referring to FIG. 24, each discharge tube 115 is formed of a cold cathode fluorescent tube that includes a generally elongated straight glass tube 134 having a circular cross section, and elongated metallic (e.g., nickel or cobalt metal) outer leads 135 which have a circular cross section and project linearly from the respective ends of the glass tube 134 and coaxially with the glass tube 134. Further included are ferrules 136 attached to the respective end portions of the glass tube 134. Mercury is encapsulated in the glass tube 134. Each end portion of the glass tube 134 is melted into a substantially hemispherical shape by heat, and thereby defines a domed portion. The outer lead 135 penetrates the domed portion.

Referring to FIGS. 25 to 27, each ferrule 136 preferably is a single-piece component, which can be formed by bending or hammering a metallic (e.g., stainless steel) plate that is formed into a predetermined shape by punching, for example. The ferrule 136 includes a body 137 and a conductive portion 140. The body 137 preferably has a substantially cylindrical shape concentric with the glass tube 134. The inner diameter of the body 137 is preferably slightly larger than the outer diameter of the glass tube 134.

Three pairs of elastic gripping portions 138A, 138B are formed on the body 137 by making slit-like cuts in portions thereof, which are arranged at even angular intervals along the circumferential direction.

A first elastic gripping portion 138A, i.e., one of a pair of elastic gripping portions 138A, 138B, is generally formed as a cantilevered portion extending posteriorly (specifically, in an oblique direction slightly leaning radially inwardly), which is capable of elastic and radial deflection with a supported point on its proximal end (or anterior end). A curved portion 139 is formed on the distal end portion (or posterior end portion) of the first elastic gripping portion 138A, so as to curve in an oblique direction leaning radially outwardly. The outer surface of the curve (or inwardly facing surface) of the curved portion 139 is provided as a contact point when abutting on the outer circumferential surface of the glass tube 134. The imaginary line that connects the contact points provided on the three first elastic gripping portions 138A forms a circle concentric with the body 137. The diameter of the imaginary circle, when the first elastic gripping portions 138A are not forced into elastic deflection or are in a free state, is set to be smaller than the outer diameter of the glass tube 134.

A second elastic gripping portion 138B, i.e., the other of the pair of elastic gripping portions 138A, 138B, is arranged circumferentially adjacent to the first elastic gripping portion 138A, and is generally formed as a cantilevered portion extending anteriorly or reversely from the first elastic gripping portion 138A (specifically, in an oblique direction slightly leaning radially inwardly), which is capable of elastic and radial deflection with a supported point on its proximal end (or posterior end). The distal end of the second elastic gripping portion 138B is provided as a contact point when abutting on the outer circumferential surface of the glass tube 134. The imaginary line that connects the contact points provided on the three second elastic gripping portions 138B forms a circle concentric with the body 137. The diameter of the imaginary circle, when the second elastic gripping portions 138B are not forced into elastic deflection or are in a free state, is preferably smaller than the outer diameter of the glass tube 134.

On the body 137, a pair of protector portions are formed as cantilevered portions protruding anteriorly from the anterior end edge thereof. The pair of protector portions are arranged circumferentially spaced apart, and extend linearly from the body 137 so as to be flush therewith. The conductive portion 140 is provided as a cantilevered portion that extends anteriorly from between the pair of protector portions. The conductive portion 140 includes a long portion 141 continuous with the anterior end of the body 137, and a cylindrical portion 142 that further projects anteriorly from the anterior end (or distal end) of the long portion 141.

The long portion 141 includes a proximal portion 141 a that extends from the body 137 so as to be flush with the body 137 and parallel or substantially parallel to the axis thereof, and further includes an intermediate portion 141 b that extends radially inwardly from the distal end of the proximal portion 141 a toward the axis of the body 137. Further included is a distal portion 141 c that extends from the distal end of the intermediate portion 141 b and parallel or substantially parallel to the axis of the body 137. The cylindrical portion 142 is connected to the distal end of the distal portion 141 c. The width of the long portion 141 is preferably sufficiently small for the length of the long portion 141. Therefore, the long portion 141 is capable of elastic deformation in the radial direction of the body 137, elastic deformation in a direction intersecting with the radial direction (and intersecting with the longitudinal direction of the long portion 141), and elastic torsional deformation around the long portion 141 itself as the axis.

The cylindrical portion 142, which can be formed by bending a portion laterally extending from the distal end of the long portion 141 into a cylindrical shape, for example, is arranged substantially coaxially with the body 137. The cylindrical portion 142 is capable of displacement around the axis of the ferrule 136 and radial displacement, due to elastic deflection of the long portion 141.

Attachment of Ferrule 136 to Glass Tube 134

Next, an assembling process for attaching a ferrule 136 to a glass tube 134 will be explained.

During the assembling process, while a ferrule 136 and a glass tube 134 are held by respective holding devices (not shown), the ferrule 136 and the glass tube 134 are moved relatively and coaxially so as to approach each other. Thereby, the body 137 is fitted onto the glass tube 134. When the body 137 begins engagement, the contact points provided on the distal end portions of the three pairs of elastic gripping portions 138A, 138B have elastic contact with the outer circumference of the glass tube 134. The contact points slide on the outer circumferential surface of the glass tube 134, as the assembling process proceeds. Then, the tip of the outer lead 135 having passed through the body 137 begins to enter the hollow of the cylindrical portion 142. When both of the holding devices have thereafter reached predetermined final positions, the ferrule 136 and the glass tube 134 are axially positioned in proper positions, resulting in the tip end portion of the outer lead 135 circumferentially surrounded by the cylindrical portion 142. At the time, the tip end portion of the outer lead 135 will not greatly protrude from the anterior end of the cylindrical portion 142. That is, it slightly protrudes out of the cylindrical portion 142, or is aligned with the anterior end of the cylindrical portion 142, or alternatively it is located within the cylindrical portion 142.

Thereafter, the cylindrical portion 142 is clamped so as to deform with diameter reduction. After being clamped, the cylindrical portion 142 is electrically conductively fixed to the outer lead 135 by welding, and consequently the ferrule 136 is integrated with the glass tube 134. Then, the assembling process terminates, and the discharge tube 115 is completed.

When the ferrule 136 is attached to the glass tube 134, the body 137 is concentrically held on the glass tube 134 due to the elastic holding function of the three pairs of elastic gripping portions 138A, 138B. A gap (airspace) is secured between the outer circumference of the glass tube 134 and the inner circumference of the body 137, so as to extend over the substantially entire circumference.

Instead of the cylindrical portion 142, a substantially U-shaped connecting portion 142 a may be provided as shown in FIGS. 36 and 37. In this case, after a glass tube 134 is fitted into a ferrule 136, the U-shaped connecting portion 142 a is bended so as to hug the outer lead 135, in order to achieve electrical connection between the outer lead 135 and the connecting portion 142 a. According to the present preferred embodiment thus including the bendable U-shaped connecting portion 142 a, electrical connectivity with the outer lead 135 can be further improved.

Mounting of Discharge Tube 115 to Relay Connectors 114

The discharge tube 115, thus assembled, is fixed to relay connectors 114. At the time of fixation, the discharge tube 115 held in a horizontal position is moved toward the front face of the chassis 113, and the end portions and the ferrules 136 of the glass tube 134 are fitted into the container rooms 123 of the relay connectors 114 from the front side. At the time, the pair of elastic pressing portions 132 are pushed by the body 137 of the ferrule 136 so as to open vertically due to elastic deflection. After the body 137 has passed through the shortest-distance portions of the pair of elastic pressing portions 132, the body 137 is pulled deep into the container room 123 due to elastic restoring forces of the elastic pressing portions 132, resulting in the body 137 abutting on the bottom of the container room 123. Then, the mounting of the discharge tube 115 is completed.

The discharge tube 115 thus mounted is held by the pairs of elastic pressing portions 132 at its end portions, and consequently is fixed to the chassis 113 via the relay terminals 131 and the holders 120 provided as the relay terminal 131 mounting bases. At the time, the weight of the discharge tube 115 is received solely by the chassis 113 via the relay connectors 114. That is, the outer leads 135 will not be under load due to the weight of the discharge tube 115.

The pair of elastic pressing portions 132 can have elastic contact with the outer circumferential surface of the body 137, and thereby the outer lead 135 is electrically conductively connected to the relay terminal 131 via the ferrule 136. Further, the glass tube 134 is held due to elastic restoring forces of the pair of elastic pressing portions 132, so as to be pressed against the concave portion 127 of the stopper 126. Therefore, when viewed along the axial direction of the discharge tube 115, the body 137 appears to be positioned so as to partially overlap with the stopper 126. That is, the end edge of the body 137 on the opposite side of the conductive portion 140 is axially positioned in proximity to the stopper 126 so as to be partially faced therewith.

The extended portion 129 is formed on the outer surface of the holder 120, which is perpendicular or substantially perpendicular to the surface of the chassis 113 and includes the escape opening 125 of the container room 123, so as to protrude from between the chassis 113 and the escape opening 125 and extend along the surface of the chassis 113. This results in a long creepage distance from the inside of the container room 123 to the front surface of the chassis 113. Thereby, a leak, from the discharge tube 115 held in the container room 123 to the chassis 113 outside the holder 120, can be prevented.

Overview of Power Board 116

As shown in FIG. 28, each power board 116 includes a circuit board 117 having a circuit formed on its back surface (i.e., the surface on the opposite side of the chassis 113), electronic components 119 mounted on the back surface of the circuit board 117, and a plurality of on-board connectors 118 mounted on the back surface of the circuit board 117.

The circuit board 117 preferably has a vertically-elongated rectangular shape as a whole, and is formed using a phenolic paper-base copper-clad laminated board (known as a phenolic paper). A plurality of fitting holes 117H having a vertically-elongated rectangular shape are formed through the circuit board 117 so as to extend from the front side to the back side. The plurality of fitting holes 117H are arranged vertically along the lateral side edge of the circuit board 117 so as to correspond to the above-described relay terminals 131 (or relay connectors 114). Each on-board connector 118 includes a housing made of synthetic resin, and an output terminal (not shown) that is completely contained in the housing and made of metal (e.g., nickel silver). The on-board connectors 118 are arranged along the lateral side edge of the circuit board 117 so as to correspond to the respective fitting holes 117H. A fitting space (not shown) is formed on the outer surface of the housing so as to correspond to the fitting hole 117H, and the output terminal is partly exposed to the fitting space.

While the circuit board 117 is kept parallel or substantially parallel to the chassis 113, the power board 116 is moved toward the chassis 113 from the back side and is fixed thereto. At the time of fixation, the wall portions 122 of the relay connectors 114 and the board connecting portions 133 arranged along the wall portions 122 penetrate the circuit board 117 through the fitting holes 117H and are inserted into the fitting spaces of the on-board connectors 118. Thereby, the on-board connectors 118 are fitted onto the relay connectors 114, and the output terminals are conductively connected to the relay terminals 131.

Operational Effects of Preferred Embodiment 2

In the present preferred embodiment 2, when a discharge tube 115 is supported on relay connectors 114, the stoppers 126 lock the ferrules 136. Therefore, the discharge tube 115 is prevented from axial movement relative to the relay connectors 114. That is, if a force is applied to the discharge tube 115 so as to cause movement to the right, the stopper 126 catches the left-adjacent ferrule 136 attached on the left end portion of the discharge tube 115 so that the movement of the discharge tube 115 to the right is restricted. If a force is applied to the discharge tube 115 so as to cause movement to the left, the stopper 126 catches the right-adjacent ferrule 136 attached on the right end portion of the discharge tube 115 so that the movement of the discharge tube 115 to the left is restricted. Thus, the axial movement of the discharge tube 115 to either right or left is restricted, and therefore the tip of the outer lead 135 is prevented from hitting the wall of the container room 123 on the opposite side of the escape opening 125.

The stopper 126 can engage with and lock the end edge of the ferrule 136, and therefore a hole that can engage with the stopper 126 is not required to be formed on the outer circumference of the ferrule 136. Thereby, processing cost can be reduced, and reduction in strength of the ferrule 136 can be prevented.

In the case of a construction in which a stopper 126 can engage with the end edge of a ferrule 136 on the side of the conductive portion 140, the conductive portion 140 extending from the end edge of the ferrule 136 may preclude the end edge of the ferrule 136 from engaging with the stopper 126, when the ferrule 136 is attached at some angle about its axis. However, in preferred embodiment 2, the stopper 126 is arranged to engage with the end edge on the opposite side of the conductive portion 140. Therefore, the conductive portion 140 will not preclude the ferrule 136 from engaging with the stopper 126, and consequently the ferrule 136 can infallibly engage with the stopper 126.

The conductive portion 140 includes a cylindrical portion 142, which can be circumferentially connected to the outer lead 135 so as to surround it. Thereby, the conductive portion 140 can be prevented from disengaging from the outer lead 135. That is, the cylindrical portion 142 will not disengage from the outer lead 135 when the cylindrical portion 142 is clamped. Therefore, the conductive portion 140 can be infallibly connected to the outer lead 135.

The margin for engagement of a ferrule 136 with a stopper 126 corresponds to half of the dimensional difference between the outer diameters of the glass tube 134 and the ferrule 136. In the present embodiment 2, ferrules 136 are concentrically held on a glass tube 134 due to the elastic gripping portions 138A, 138B. Therefore, if the ferrule 136 is set to be large, a large dimensional difference can be secured between the inner diameter thereof and the outer diameter of the glass tube 134. Thereby, the margin for engagement of the ferrule 136 with the stopper 126 can be increased, resulting in reliable restriction of movement of the discharge tube 115.

The concave portion 127 is preferably provided on a stopper 126, so as to abut on the outer circumference of a glass tube 134 when the ferrule 136 engages with the stopper 126. Further, the pair of elastic pressing portions 132 capable of pressing the discharge tube 115 toward the concave portion 127 side are provided in the relay connector 114. Specifically, the pair of elastic pressing portions 132 press the discharge tube 115 toward the concave portion 127 side, obliquely from above and obliquely from below, i.e., vertically symmetrically. Thereby, the glass tube 134 is prevented from disengaging from the concave portion 127, and therefore the engagement of the ferrule 136 with the stopper 126 can be reliably maintained.

The relay connector 114 is preferably formed by mounting a relay terminal 131 in a holder 120 made of synthetic resin. In preferred embodiment 2, the stopper 126 is preferably provided on the synthetic-resin holder 120. Therefore, a stopper is not required to be formed on the relay terminal 131, and thereby the material for manufacturing the relay terminals 131 can be reduced. Considering that the material cost for synthetic resin is generally lower than that for metal, the material cost for relay connectors 114 can be reduced according to preferred embodiment 2.

Preferred Embodiment 3

Next, preferred embodiment 3 of the present invention will be explained with reference to FIGS. 29 to 35. In preferred embodiment 3, the constructions of a structure to support a discharge tube 115 differ from those of preferred embodiment 2. The other constructions are similar to preferred embodiment 2. Therefore, the same constructions are designated by the same symbols, and explanations for the constructions, operations and effects thereof are omitted.

Overview of Grounding Member 150

In preferred embodiment 2, the end portions of a discharge tube 115 are supported by relay connectors 114, each of which includes a holder 120 and a relay terminal 131. In preferred embodiment 3, as shown in FIGS. 29 and 30, one of the end portions of a discharge tube 115 is supported by the same relay connector 114 as in preferred embodiment 2, while the other end portion of the discharge tube 115 is supported by a grounding member 150.

As shown in FIG. 32, the grounding member 150 includes an elongated support plate 151 fixed to the chassis 113 so as to be along one of the lateral edge portions thereof, and further includes a plurality of grounding terminals 152 conductively mounted on the front surface of the support plate 151. Mounting holes 151H are formed through the support plate 151 so as to correspond three-to-one with the grounding terminals 152. The support plate 151 preferably is made of a substrate or a metallic plate.

On the other hand, as shown in FIG. 33, each grounding terminal 152, which can be formed by bending a metallic (e.g., nickel silver) plate that is formed into a predetermined shape by punching, for example, includes a base portion 153 and a pair of elastic pressing portions 154 which extend vertically symmetrically from the respective upper and lower edge portions of the base portion 153 to the front side. Further included is a stopper 155 that extends from one of the lateral edge portions of the base portion 153 to the front side.

The pair of elastic pressing portions 154 are provided on the lateral edge portion on the opposite side of the stopper 155, so as to form bulging curves toward each other. The elastic pressing portions 154 are capable of elastic deflection so as to increase the distance therebetween. The minimum distance between the pair of elastic pressing portions 154, when the elastic pressing portions 154 are free from elastic deflection, is preferably smaller than the outer diameter of the glass tube 134 of a discharge tube 115.

The stopper 155 is raised from the base portion 153, so as to define a right angle with the axis of the discharge tube 115. A concave portion 156 is preferably provided on the stopper 155, so as to sag in a substantially circular arc. On a relay connector 114 of preferred embodiment 2, a pair of guiding portions 128 are raised from the respective upper and lower sides of the concave portion 127 of the stopper 126. However, in preferred embodiment 3, the heights of portions raised from the respective upper and lower sides of the concave portion 156 of the base portion 153 are reduced to be short. That is, elements corresponding the guiding portions 128 of the embodiment 2 are not provided. Therefore, metallic material required for grounding terminals 152 can be reduced, compared to including guiding portions.

Three leg portions 157 are further formed on the base portion 153, so as to be integrated therewith. Two of the three leg portions 157 are provided between the elastic pressing portions 154 and the stopper 155, so as to project from the respective upper and lower edge portions of the base portion 153 to the opposite side of the elastic pressing portions 154 or the stopper 155 (i.e., to the back side). The remaining one of the leg portions 157 is provided on the lateral edge of the base portion 153 on the opposite side of the stopper 155, so as to project from the intermediate position between the elastic pressing portions 154 to the opposite side of the elastic pressing portions 154 or the stopper 155 (i.e., to the back side).

The grounding terminal 152 is not housed in a member such as a plastic housing, i.e., barely provided as shown in FIG. 34, and is conductively fixed to the support plate 151 by soldering or other suitable method so that its leg portions 157 penetrate through the mounting holes 151H. Thus, the plurality of grounding terminals 152 are mounted to the common support plate 151, and thereby are conductively connected to one another via the support plate 151. Power boards are not connected to the grounding members 150, and the support plate 151 is conductively connected to the chassis 113.

Mounting of Discharge Tube 115 to Grounding Terminal 152

When a discharge tube 115 is fixed to a grounding terminal 152, referring to FIG. 35, the discharge tube 115 held in a horizontal position is moved toward the front surface of the chassis 113, and the end portion and the ferrule 136 of the glass tube 134 are fitted between the pair of upper and lower elastic pressing portions 154 from the front side. At the time, the pair of elastic pressing portions 154 are pushed by the body 137 of the ferrule 136 so as to open vertically due to elastic deflection. After the body 137 has passed through the shortest-distance portions of the pair of elastic pressing portions 154, the body 137 is pulled toward the base portion 153 side due to elastic restoring forces of the elastic pressing portions 154, resulting in the body 137 abutting on the base portion 153. Then, the fixation of the discharge tube 115 is completed. The other end portion of the discharge tube 115 is fixed to a relay connector 114 in a similar manner to preferred embodiment 2.

The discharge tube 115 thus mounted is supported by the relay connector 114 and the grounding member 150 at its respective end portions. The pairs of elastic pressing portions 132, 154 can have elastic contact with the outer circumferential surfaces of the bodies 137 of the ferrules 136, and thereby the outer leads 135 are electrically conductively connected to the relay terminal 131 and the grounding terminal 152 via the ferrules 136. Further, the glass tube 134 is held due to elastic restoring forces of the pairs of elastic pressing portions 132, 154, so as to be pressed against the concave portions 127, 156 of the stoppers 126, 155. Therefore, when viewed along the axial direction of the discharge tube 115, the body 137 appears to be positioned so as to partially overlap with the stopper 126 or 155. That is, the end edge of the body 137 on the opposite side of the conductive portion 140 is axially positioned in proximity to the stopper 126 or 155 so as to be partially faced therewith.

As shown in FIGS. 38 and 39, protector portions 551 may be provided on the grounding terminal 152. Each protector portion 551 includes a restricting portion 552 for an elastic pressing portion, and further includes an abutting portion 553 arranged to abut the support plate. When the grounding terminal 152 is mounted and fixed to the support plate 151, the abutting portions 553 abut on or are located close to the support plate 151. If some kind of external force is applied to the elastic pressing portions 154 so that they are pushed to open, they first become in contact with the restricting portions 552 during the course of opening. The abutting portions 553 serve as supports for preventing the protector portions 551 from collapsing, when an additional load is thereafter applied. The protector portions 551 are connected to the feet of the elastic pressing portions 154, and therefore the abutting portions 553 are preferably lateral to the connection portion in order that the abutting portions 553 work. Note that abutting portions 553 located at a longer distance from the connection portion are more effective.

Operational Effects of Preferred Embodiment 3

In the present preferred embodiment 3, when a discharge tube 115 is supported on a relay connector 114 and a grounding member 150, the stopper 126 of the holder 120 and the stopper 155 of the grounding terminal 152 lock the ferrules 136 on the respective ends of the discharge tube 115. Therefore, the discharge tube 115 is secure from axial movement relative to the relay connector 114.

That is, if a force is applied to the discharge tube 115 so as to cause movement from the relay connector 114 side to the grounding member 150 side, the ferrule 136 attached on the end portion of the discharge tube 115 on the relay connector 114 side is caught by the stopper 126 of the holder 120 so that the movement of the discharge tube 115 to the grounding member 150 side is restricted. If a force is applied to the discharge tube 115 so as to cause movement from the grounding member 150 side to the relay connector 114 side, the ferrule 136 attached on the end portion of the discharge tube 115 on the grounding member 150 side is caught by the stopper 155 of the grounding terminal 152 so that the movement of the discharge tube 115 to the relay connector 114 side is restricted. Thus, the axial movement of the discharge tube 115 to either right or left is restricted, and therefore the tip of the outer lead 135 is secure from hitting the wall of the container room 123 on the opposite side of the escape opening 125 or hitting the sidewall of the chassis 113.

The concave portion 156 is preferably provided on the stopper 155 of a grounding terminal 152, so as to abut on the outer circumference of a glass tube 134 when the ferrule 136 is engaged with the stopper 155. Further, the pair of elastic pressing portions 154 capable of pressing the discharge tube 115 toward the concave portion 156 side are provided on the grounding terminal 152. Specifically, the pair of elastic pressing portions 154 press the discharge tube 115 toward the concave portion 156 side, obliquely from above and obliquely from below, i.e., vertically symmetrically. Thereby, the glass tube 134 is prevented from disengaging from the concave portion 156, and therefore the engagement of the ferrule 136 with the stopper 155 can be reliably maintained.

On the grounding member 150, the stoppers 155 are integrated with the respective grounding terminals 152 to provide conductive connection to the ferrules 136. Thereby, the number of components can be reduced in preferred embodiment 3, compared to including stoppers provided as separate members from the grounding terminals.

Other Preferred Embodiments

The present invention is not limited to the preferred embodiments explained in the above description made with reference to the drawings. The following preferred embodiments may be included in the technical scope of the present invention, for example.

The output terminal is not limited to being formed of a female component, but rather may be formed of a male component. The output terminal formed of a male component may partly penetrate through the fitting hole, so as to project to the front side of the circuit board.

The terminal that penetrates through the fitting hole is not limited to the relay terminal. The output terminal may be arranged to solely penetrate through the fitting hole, or alternatively, both of the relay terminal and the output terminal may be arranged to penetrate through the fitting hole.

The connecting portion of the output terminal is not limited to being capable of elastic deflection. A connecting portion not prone to elastic deflection may be provided, instead. In this case, the board connecting portion of the relay terminal may be provided so as to be capable of elastic deflection, or alternatively, may be provided so as not to be prone to elastic deflection.

The structure or elements arranged to prevent the displacement of the output terminal is not limited to the positioning portions provided to lock the output terminal, but rather may be achieved by increasing the flexural rigidity of the output terminal.

In order to absorb the displacement of relay terminals from output terminals, relay terminals having an elongated shape substantially perpendicular to the array direction of the on-board connectors, and output terminals having a plate-shaped configuration parallel or substantially parallel to the array direction may be provided.

On each on-board connector, the output terminal may be arranged on an area of the housing closer to the edge portion of the circuit board, resulting in narrow sectional arrangement. Alternatively, the output terminal may be arranged to extend, from the end portion of the housing closer to the edge portion of the circuit board, to the end edge farther from the edge portion of the circuit board.

The housing may be eliminated from each on-board connector, so that the output terminal is barely provided on the circuit board.

The circuit board of each power board is not limited to a phenolic paper-base copper-clad laminated board, but rather may be formed of a plate made of glass epoxy or ceramics.

The output terminal may be formed into a predetermined shape simply by punching a metallic material, without bending.

The display panel of the display device is not limited to having TFTs as switching elements, but rather may include, as switching elements, elements other than TFTs such as MIM (Metal Insulator Metal) elements.

The display device is not limited to a liquid crystal display device. Various display devices requiring a lighting device on the back side of a display panel can be included.

The material for housings is not limited to synthetic resin. An insulating material other than synthetic resin can be used, instead.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

1-19. (canceled)
 20. A power board to be mounted to a back side of a chassis having a substantially plate-shaped configuration, comprising: a circuit board capable of being arranged substantially parallel to said chassis; and an on-board connector mounted to said circuit board; wherein an output terminal of said on-board connector is arranged to be connected to a relay terminal provided on said chassis, so that power is supplied to a discharge tube arranged on a front side of said chassis; a fitting hole is formed through said circuit board so as to extend from a front surface to a back surface thereof; and said on-board connector is mounted to the back surface of said circuit board, and is positioned to correspond to said fitting hole.
 21. A power board according to claim 20, wherein said on-board connector includes a housing made of an insulating material, and said output terminal is at least partly held in said housing.
 22. A power board according to claim 21, wherein an engaging recess is formed on said housing so as to have an opening corresponding to said fitting hole, and said output terminal is arranged in said engaging recess.
 23. A power board according to claim 22, wherein said output terminal is capable of being connected to said relay terminal when said relay terminal is fitted into said engaging recess, and said relay terminal when being fitted into said engaging recess is movable, and a connection between said relay terminal and said output terminal is maintained when said relay terminal is displaced.
 24. A power board according to claim 22, wherein a positioning portion, which is capable of locking said output terminal so that displacement of said output terminal along an inside surface of said engaging recess is restricted, is provided on said inside surface.
 25. A power board according to claim 21, wherein said output terminal includes a proximal portion fixed to said housing, a flexible portion extending from said proximal portion and being capable of elastic deflection, and a connecting portion extending from said flexible portion and having a substantially U-shape capable of elastically pinching said relay terminal, and said connecting portion includes two strip portions, and a free-end-side strip portion of the two strip portions on an opposite side of said flexible portion is capable of contact with said relay terminal.
 26. A power board according to claim 20, wherein a plurality of on-board connectors as said on-board connector are arranged in a line so as to be capable of corresponding to a plurality of relay terminals as said relay terminal, said output terminal includes a connecting portion is arranged to be capable of contact with said relay terminal that has a substantially plate-shaped configuration having a width larger than that of said connecting portion and to be arranged substantially parallel to an array direction of said plurality of on-board connectors.
 27. A power board according to claim 21, wherein said on-board connector is arranged along an edge portion of said circuit board, and said output terminal is arranged on an area of said housing on an opposite side of said edge portion, so that a sectional arrangement is provided.
 28. An on-board connector, to be mounted to a circuit board in order to provide a power board that is capable of being mounted to a back side of a chassis having a substantially plate-shaped configuration so that said circuit board is arranged substantially parallel to said chassis; said on-board connector comprising an output terminal that is capable of being connected to a relay terminal provided on said chassis so that power is supplied to a discharge tube arranged on a front side of said chassis; wherein said on-board connector is capable of being mounted to a back surface of said circuit board and being positioned to correspond to a fitting hole that is formed through said circuit board so as to extend from a front surface to the back surface thereof.
 29. An on-board connector according to claim 28, further comprising a housing made of an insulating material, wherein said output terminal is at least partly held in said housing.
 30. An on-board connector according to claim 29, wherein an engaging recess is formed on said housing so as to have an opening capable of being arranged to correspond to said fitting hole, and said output terminal is arranged in said engaging recess.
 31. An on-board connector according to claim 30, wherein said output terminal is capable of being connected to said relay terminal when said relay terminal is fitted into said engaging recess, and said relay terminal when being fitted into said engaging recess is movable, and a connection between said relay terminal and said output terminal is maintained when said relay terminal moves into displacement.
 32. An on-board connector according to claim 30, wherein a positioning portion, which is capable of locking said output terminal so that displacement of said output terminal along an inside surface of said engaging recess is restricted, is provided on said inside surface.
 33. An on-board connector according to claim 29, wherein said output terminal includes a proximal portion fixed to said housing, a flexible portion extending from said proximal portion and being capable of elastic deflection, and a connecting portion extending from said flexible portion and having a substantially U-shape capable of elastically pinching said relay terminal, and said connecting portion includes two strip portions, and a free-end-side strip portion of the two strip portions on an opposite side of said flexible portion is capable of contact with said relay terminal.
 34. An on-board connector according to claim 29, wherein a plurality of housings as said housing are arranged in a line so as to be capable of corresponding to a plurality of relay terminals as said relay terminal, said output terminal includes a connecting portion that is arranged to be capable of contact with said relay terminal that has a substantially plate-shaped configuration having a width larger than that of said connecting portion and to be arranged substantially parallel to an array direction of said plurality of on-board connectors.
 35. An on-board connector according to claim 29, wherein said housing is to be arranged along an edge portion of said circuit board, and said output terminal is arranged on an area of said housing capable of being positioned on an opposite side of said edge portion, so that a sectional arrangement is provided.
 36. A lighting device for a display device, comprising: a chassis having a substantially plate-shaped configuration; a discharge tube arranged on a front side of said chassis; and a power board mounted to a back side of said chassis; wherein said power board includes a circuit board arranged substantially parallel to said chassis, and an on-board connector mounted to a back surface of said circuit board; a fitting hole is formed through said circuit board so as to extend from a front surface to the back surface thereof, and said on-board connector is positioned to correspond to said fitting hole; and an output terminal of said on-board connector is connected to a relay terminal provided on said chassis, so that power is supplied to said discharge tube.
 37. A display device comprising: a lighting device; and a display panel arranged on a front side of said lighting device; wherein said lighting device includes: a chassis having a substantially plate-shaped configuration; a discharge tube arranged on a front side of said chassis; and a power board mounted to a back side of said chassis; wherein said power board includes a circuit board arranged substantially parallel to said chassis, and an on-board connector mounted to a back surface of said circuit board; a fitting hole is formed through said circuit board so as to extend from a front surface to the back surface thereof, and said on-board connector is positioned to correspond to said fitting hole; and an output terminal of said on-board connector is connected to a relay terminal provided on said chassis, so that power is supplied to said discharge tube.
 38. A television receiver comprising a display device that includes: a lighting device; and a display panel arranged on a front side of said lighting device; wherein said lighting device includes: a chassis having a substantially plate-shaped configuration; a discharge tube arranged on a front side of said chassis; and a power board mounted to a back side of said chassis; wherein said power board includes a circuit board arranged substantially parallel to said chassis, and an on-board connector mounted to a back surface of said circuit board; a fitting hole is formed through said circuit board so as to extend from a front surface to the back surface thereof, and said on-board connector is positioned to correspond to said fitting hole; and an output terminal of said on-board connector is connected to a relay terminal provided on said chassis, so that power is supplied to said discharge tube. 